The present invention relates to xanthine derivatives or pharmaceutically acceptable salts thereof having adenosine A.sub.1 receptor antagonizing activity, and thus exhibiting diuretic effect, renal-protecting effect, bronchodilatory effect, cerebral function improving effect, and anti-dementia effect.
In relation to the compounds of the present invention, 8-(1-adamantyl)-1,3,7-trimethylxanthine is disclosed in Tetrahedron Letters, 27, 6339-6340 (1986). However, nothing is mentioned on its pharmacological effect in the literature.
Also, it is known that a xanthine derivative represented by the formula ##STR3## (wherein R.sup.A and R.sup.B are lower alkyl, Y.sup.A is a single bond or alkylene, and n.sup.a is 0 or 1) has activity of selectively antagonizing adenosine A.sub.1 receptor and thus shows renal-protecting effect, and bronchodilatory effect (Japanese Published Unexamined Patent Application No. 173889/91); and cerebral function improving effect (Japanese Published Unexamined Patent Application No. 270222/92). Further, it is known that a xanthine derivative represented by the formula ##STR4## (wherein R.sup.C and R.sup.D are hydroxy-substituted or unsubstituted lower alkyl, and R.sup.E is substituted or unsubstituted tricycloalkyl of C.sub.7 -C.sub.12) shows anti-ulcerative effect, etc. (Japanese Published Unexamined Patent Application No. 58913/93), but no specific examples of the hydroxy-substituted xanthine derivatives are disclosed in the publication.
It is also known that a xanthine derivative represented by the formula ##STR5## (wherein, R.sup.F and R.sup.G are the same or different, and each represent hydroxy-substituted or unsubstituted lower alkyl, and R.sup.H is dihydroxyalkyl or ##STR6## [wherein, X is O, S or NR.sup.P (wherein R.sup.P is hydrogen, lower alkyl or lower acyl), m.sup.a and n.sup.b are the same or different and each represent an integer of from 1 to 5] shows central nervous system stimulating effect (U.S. Pat. No. 4,755,517). It is known that a xanthine derivative represented by the formula ##STR7## (wherein, R.sup.J is methyl, ethyl or propyl, R.sup.K is 2-hydroxypropyl, and R.sup.L is methyl or propyl) shows antiallergic effect (Japanese Published Unexamined Patent Application No. 79296/79) and that a xanthine derivative represented by the formula ##STR8## [wherein at least one of R.sup.M and R.sup.O is (.omega.-1)-hydroxyalkyl having from three to eight carbon atoms, or when only one of R.sup.M and R.sup.O is (.omega.-1)-hydroxyalkyl, the other is hydrogen or lower alkyl, and R.sup.N is lower alkyl] has activity of reducing nephrotoxicity (Japanese Published Unexamined Patent Application No. 90028/91).